Stephen, I am just using the 3M tape, I did sand the ends of the pipe very
flat
with no rounding of the edges.
I do clean the end of the pipe with acetone prior to shooting.
Wayne Petersen of BYU uses the couple system similar to Skinners setup
with a square of space blanket coated mylar as his rear membrane and a
plastic
thread protector cap [you know those little blue throw away thingies] for
his front cap. This system of Waynes is very strong [mylar] and very
repeatable, you could
substitute a thin aluminum cap on the front so long as it was tethered.
Good luck. Zig